A plant tag that says “full sun” is not really talking about your balcony. It was written for someone with a backyard, unobstructed sky, and no concrete wall radiating heat back at 6 p.m. Balconies change the math, and most of the frustration people run into with container gardening traces back to this one mismatch …

A woman messaged me last spring with a photo of six dead basil plants lined up like a small funeral procession. Her balcony faced south, she told me, so she figured full sun was a given. What she hadn’t accounted for was the building across the street, which shaded her railing until almost noon, then …